Abstract:

A system that includes a turbine fuel nozzle comprising an air-fuel
premixer. The air-fuel premixed includes a swirl vane configured to swirl
fuel and air in a downstream direction, wherein the swirl vane comprises
an internal coolant path from a downstream end portion in an upstream
direction through a substantial length of the swirl vane.

Claims:

1. A system, comprising:a fuel nozzle, comprising:a central body;an outer
tube disposed about the central body;an air path disposed between the
central body and the outer tube;a vane disposed in the air path, wherein
the vane comprises a fuel inlet,a fuel outlet, and a divider disposed
between the fuel inlet and the fuel outlet; anda fuel path extending
through the central body to the fuel inlet into the vane, wherein the
fuel path extends through the vane in a non-straight direction about the
divider from the fuel inlet to the fuel outlet.

2. The system of claim 1, wherein the divider is disposed in the vane
axially between a downstream cavity having the fuel inlet and an upstream
cavity having the fuel outlet.

3. The system of claim 2, wherein the upstream cavity comprises a bypass
adapted to channel fuel from the fuel path extending through the central
body directly into the upstream cavity.

4. The system of claim 2, wherein the downstream cavity comprises a bypass
adapted to channel fuel from the fuel path extending through the central
body directly into the downstream cavity.

5. The system of claim 2, wherein the divider comprises a crossover
passage through the divider, wherein the crossover passage is adapted to
channel fuel from the downstream cavity directly into the upstream
cavity.

6. The system of claim 1, wherein the vane is curved to create swirl in
the air path.

7. The system of claim 1, wherein the central body comprises a fuel
passage extending a downstream axial direction and a reverse flow passage
extending in an upstream axial direction, wherein the central body
extends axially downstream away from the vane.

8. The system of claim 1, wherein the fuel outlet is angularly positioned
on an outer surface of the vane.

9. The system of claim 1, comprising a combustor having the fuel nozzle, a
turbine engine having the fuel nozzle, or a combination thereof.

10. The system of claim 1, wherein the fuel path extends through a
substantial length of the vane in an upstream direction from the fuel
inlet to the fuel outlet, and the upstream direction is generally
opposite from a downstream direction of air flow along the air path.

11. A gas turbine fuel nozzle, comprising:a central body comprising a
multi-directional flow passage having a first flow passage configured to
channel fuel in a first axial direction, and a second flow passage
configured to channel fuel in a second axial direction opposite from the
first axial direction;an outer tube disposed about the central body;an
air path disposed between the central body and the outer tube;a vane
disposed in the air path, wherein the vane comprises:a fuel inlet
disposed in a downstream cavity of the vane relative to the first axial
direction;a fuel outlet disposed in an upstream cavity of the vane
relative to the first axial direction;a fuel path from the downstream
cavity to the upstream cavity; anda bypass configured to channel fuel to
the upstream cavity independent from the fuel path.

12. The gas turbine fuel nozzle of claim 11, wherein the bypass is
configured to channel fuel from the multi-directional flow passage
extending through the central body directly into the downstream cavity.

13. The gas turbine fuel nozzle of claim 11, wherein the bypass is
configured to channel fuel from the multi-directional flow passage
extending through the central body directly into the upstream cavity.

14. The gas turbine fuel nozzle of claim 13, comprising a second bypass
configured to channel fuel from the multi-directional flow passage
extending through the central body directly into the downstream cavity.

15. The gas turbine fuel nozzle of claim 11, comprising a divider disposed
in the vane axially between the downstream cavity having the fuel inlet
and the upstream cavity having the fuel outlet, wherein the divider
routes the fuel path in a non-linear direction from the fuel inlet to the
fuel outlet.

16. The gas turbine fuel nozzle of claim 17, wherein the divider comprises
a crossover passage through the divider, wherein the crossover passage is
adapted to channel fuel from the downstream cavity directly into the
upstream cavity.

17. The gas turbine fuel nozzle of claim 11, wherein the vane comprises an
airfoil shaped hollow body having the fuel inlet leading into the
downstream cavity near a downstream tip of the vane, and the fuel path
extends through the vane in the second axial direction along a
substantial length of the vane.

18. A system, comprising:a turbine fuel nozzle, comprising:an air-fuel
premixer having a swirl vane configured to swirl fuel and air in a
downstream direction, wherein the swirl vane comprises an internal
coolant path from a downstream end portion in an upstream direction
through a substantial length of the swirl vane.

19. The system of claim 18, wherein the internal coolant path comprises a
fuel path leading to one or more fuel injection ports.

20. The system of claim 18, wherein the internal coolant path comprises a
non-linear path through the swirl vane.

Description:

BACKGROUND OF THE INVENTION

[0002]The subject matter disclosed herein relates to a gas turbine
premixer configured to premix fuel and air for combustion in a combustor
of a gas turbine engine. More particularly, the subject matter disclosed
herein relates to a cooling system for the gas turbine premixer.

[0003]A gas turbine engine combusts a mixture of fuel and air to generate
hot combustion gases, which in turn drive one or more turbines. In
particular, the hot combustion gases force turbine blades to rotate,
thereby driving a shaft to rotate one or more loads, e.g., electrical
generator. As appreciated, a flame develops in a combustion zone having a
combustible mixture of fuel and air. Unfortunately, the flame can
sometimes become located on or near surfaces not designed to be in close
proximity to the reaction, which can result in damage due to the heat of
combustion. This phenomenon in a fuel/air premixer is generally referred
to as flame holding. For example, the flame holding may occur on or near
a fuel-air premixer, which can rapidly fail due to the heat of
combustion. Likewise, the flame can sometimes propagate upstream from the
combustion zone, and cause damage to various components due to the heat
of combustion. This phenomenon is generally referred to as flashback.

BRIEF DESCRIPTION OF THE INVENTION

[0004]Certain embodiments commensurate in scope with the originally
claimed invention are summarized below. These embodiments are not
intended to limit the scope of the claimed invention, but rather these
embodiments are intended only to provide a brief summary of possible
forms of the invention. Indeed, the invention may encompass a variety of
forms that may be similar to or different from the embodiments set forth
below.

[0005]In a first embodiment, a system includes a fuel nozzle, comprising a
central body, an outer tube disposed about the central body, an air path
disposed between the central body and the outer tube, a vane disposed in
the air path, wherein the vane comprises a fuel inlet, a fuel outlet, and
a divider disposed between the fuel inlet and the fuel outlet, and a fuel
path extending through the central body to the fuel inlet into the vane,
wherein the fuel path extends through the vane in a non-straight
direction about the divider from the fuel inlet to the fuel outlet.

[0006]In a second embodiment, an gas turbine fuel nozzle including a
central body comprising a multi-directional flow passage having a first
flow passage configured to channel fuel in a first axial direction, and a
second flow passage configured to channel fuel in a second axial
direction opposite from the first axial direction, an outer tube disposed
about the central body, an air path disposed between the central body and
the outer tube, a vane disposed in the air path, wherein the vane
comprises a fuel inlet disposed in a downstream cavity of the vane
relative to the first axial direction, a fuel outlet disposed in an
upstream cavity of the vane relative to the first axial direction, a fuel
path from the downstream cavity to the upstream cavity, and a bypass
configured to channel fuel to the upstream cavity independent from the
fuel path.

[0007]In a third embodiment, a system includes a turbine fuel nozzle
comprising an air-fuel premixer having a swirl vane configured to swirl
fuel and air in a downstream direction, wherein the swirl vane comprises
an internal coolant path from a downstream end portion in an upstream
direction through a substantial length of the swirl vane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]These and other features, aspects, and advantages of the present
invention will become better understood when the following detailed
description is read with reference to the accompanying drawings in which
like characters represent like parts throughout the drawings, wherein:

[0009]FIG. 1 a schematic block diagram of an embodiment of an integrated
gasification combined cycle (IGCC) power plant;

[0010]FIG. 2 is a cutaway side view of a gas turbine engine, as shown in
FIG. 1, in accordance with an embodiment of the present technique;

[0011]FIG. 3 is a perspective view of a head end of a combustor of the gas
turbine engine, as shown in FIG. 2, illustrating multiple fuel nozzles in
accordance with certain embodiments of the present technique;

[0012]FIG. 4 is a cross-sectional side view of a fuel nozzle, as shown in
FIG. 3, illustrating a premixer with internal cooling in accordance with
certain embodiments of the present technique;

[0013]FIG. 5 is a perspective cutaway view of the fuel nozzle, as shown in
FIG. 4, illustrating internal cooling in a swirl vane of the premixer in
accordance with certain embodiments of the present technique;

[0014]FIG. 6 is a cutaway side view of the premixer, as shown in FIG. 5,
illustrating internal cooling in a swirl vane in accordance with certain
embodiments of the present technique;

[0015]FIG. 7 is a cutaway side view of the premixer, as shown in FIG. 5,
illustrating internal cooling in a swirl vane in accordance with certain
embodiments of the present technique; and

[0016]FIG. 8 is a cutaway side view of the premixer, as shown in FIG. 5,
illustrating internal cooling in a swirl vane in accordance with certain
embodiments of the present technique;

DETAILED DESCRIPTION OF THE INVENTION

[0017]One or more specific embodiments of the present invention will be
described below. In an effort to provide a concise description of these
embodiments, all features of an actual implementation may not be
described in the specification. It should be appreciated that in the
development of any such actual implementation, as in any engineering or
design project, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that such a
development effort might be complex and time consuming, but would
nevertheless be a routine undertaking of design, fabrication, and
manufacture for those of ordinary skill having the benefit of this
disclosure.

[0018]When introducing elements of various embodiments of the present
invention, the articles "a," "an," "the," and "said" are intended to mean
that there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean that
there may be additional elements other than the listed elements.

[0019]In certain embodiments, as discussed in detail below, a gas turbine
engine includes one or more fuel nozzles with internal cooling passages
to resist thermal damage associated with flashback and/or flame holding.
In particular, the fuel nozzle may include one or more internal cooling
passages in a fuel-air premixer, e.g., a swirl vane configured to
facilitate fuel-air mixing prior to entry of the fuel and air into a
combustion zone. For example, the fuel nozzle may include a plurality of
swirl vanes in a circumferential arrangement, wherein the internal
cooling passages extend along substantially an entire axial length of the
swirl vanes. In certain embodiments, each internal cooling passage may
route a coolant from a downstream end portion to an upstream end portion
of the respective swirl vane, thereby providing maximum cooling at the
downstream end portion. For example, the coolant may be the fuel, which
may flow through the swirl vanes from the downstream end portion to the
upstream end portion. At the upstream end portion, the fuel may exit from
the swirl vane through one or more fuel ports, which direct the fuel into
an air flow to create a fuel-air mixture. Thus, the fuel flow serves two
functions, acting both as a fuel source for combustion and also acting as
a heat exchanger medium to transfer heat away from the swirl vane prior
to its injection into the air stream

[0020]In certain embodiments, each internal cooling passage may receive a
first portion of the fuel flow at the downstream end portion, while also
receiving a second portion of the fuel flow at the upstream end portion.
In other words, the second portion of the fuel flow may be described as a
bypass flow, which does not flow along the entire axial length of the
swirl vane from the downstream end portion to the upstream end portion.
Thus, the system may control the first and second portions of the fuel
flow to provide adjustments to the fuel system pressure drop, convective
heat transfer coefficients, and fuel distribution to the fuel ports.

[0021]In the event of flame holding or flashback, the internal cooling
passages provide thermal resistance, insulation, or protection against
thermal damage for an amount of time sufficient to detect and correct the
situation. For example, the internal cooling passages may provide thermal
protection for at least greater than approximately 15, 30, 45, 60, 75,
90, or more seconds. Furthermore, the internal cooling passages, using
fuel as the coolant or heat exchanger medium, provide a built-in failsafe
in the event of thermal damage. In particular, the thermal damage may
occur at the downstream end portion (e.g., tip) of the swirl vane,
thereby causing the fuel to flow directly from the internal cooling
passage into the air flow. As a result, the fuel flow is substantially or
entirely detoured away the fuel ports at the upstream end portion of the
swirl vane, thereby substantially or entirely eliminating any fuel-air
mixture upstream from the thermal damage at the downstream end portion
(e.g., tip) of the swirl vane. Thus, the thermal damage at the downstream
end portion (e.g., open tip) of the swirl vane may reduce or eliminate
the possibility of any further damage to the fuel nozzle (e.g., further
upstream).

[0022]FIG. 1 is a diagram of an embodiment of an integrated gasification
combined cycle (IGCC) system 100 that may produce and burn a synthetic
gas, i.e., syngas. Elements of the IGCC system 100 may include a fuel
source 102, such as a solid feed, that may be utilized as a source of
energy for the IGCC. The fuel source 102 may include coal, petroleum
coke, biomass, wood-based materials, agricultural wastes, tars, coke oven
gas and asphalt, or other carbon containing items.

[0023]The solid fuel of the fuel source 102 may be passed to a feedstock
preparation unit 104. The feedstock preparation unit 104 may, for
example, resize or reshaped the fuel source 102 by chopping, milling,
shredding, pulverizing, briquetting, or palletizing the fuel source 102
to generate feedstock. Additionally, water, or other suitable liquids may
be added to the fuel source 102 in the feedstock preparation unit 104 to
create slurry feedstock. In other embodiments, no liquid is added to the
fuel source, thus yielding dry feedstock.

[0024]The feedstock may be passed to a gasifier 106 from the feedstock
preparation unit 104. The gasifier 106 may convert the feedstock into a
syngas, e.g., a combination of carbon monoxide and hydrogen. This
conversion may be accomplished by subjecting the feedstock to a
controlled amount of steam and oxygen at elevated pressures, e.g., from
approximately 20 bar to 85 bar, and temperatures, e.g., approximately 700
degrees Celsius to 1600 degrees Celsius, depending on the type of
gasifier 106 utilized. The gasification process may include the feedstock
undergoing a pyrolysis process, whereby the feedstock is heated.
Temperatures inside the gasifier 106 may range from approximately 150
degrees Celsius to 700 degrees Celsius during the pyrolysis process,
depending on the fuel source 102 utilized to generate the feedstock. The
heating of the feedstock during the pyrolysis process may generate a
solid, (e.g., char), and residue gases, (e.g., carbon monoxide, hydrogen,
and nitrogen). The char remaining from the feedstock from the pyrolysis
process may only weigh up to approximately 30% of the weight of the
original feedstock.

[0025]A combustion process may then occur in the gasifier 106. The
combustion may include introducing oxygen to the char and residue gases.
The char and residue gases may react with the oxygen to form carbon
dioxide and carbon monoxide, which provides heat for the subsequent
gasification reactions. The temperatures during the combustion process
may range from approximately 700 degrees Celsius to 1600 degrees Celsius.
Next, steam may be introduced into the gasifier 106 during a gasification
step. The char may react with the carbon dioxide and steam to produce
carbon monoxide and hydrogen at temperatures ranging from approximately
800 degrees Celsius to 1100 degrees Celsius. In essence, the gasifier
utilizes steam and oxygen to allow some of the feedstock to be "burned"
to produce carbon monoxide and release energy, which drives a second
reaction that converts further feedstock to hydrogen and additional
carbon dioxide.

[0026]In this way, a resultant gas is manufactured by the gasifier 106.
This resultant gas may include approximately 85% of carbon monoxide and
hydrogen in equal proportions, as well as CH4, HCl, HF, COS,
NH3, HCN, and H2S (based on the sulfur content of the
feedstock). This resultant gas may be termed dirty syngas, since it
contains, for example, H2S. The gasifier 106 may also generate
waste, such as slag 108, which may be a wet ash material. This slag 108
may be removed from the gasifier 106 and disposed of, for example, as
road base or as another building material. To clean the dirty syngas, a
gas cleaning unit 110 may be utilized. The gas cleaning unit 110 may
scrub the dirty syngas to remove the HCl, HF, COS, HCN, and H2S from
the dirty syngas, which may include separation of sulfur 111 in a sulfur
processor 112 by, for example, an acid gas removal process in the sulfur
processor 112. Furthermore, the gas cleaning unit 110 may separate salts
113 from the dirty syngas via a water treatment unit 114 that may utilize
water purification techniques to generate usable salts 113 from the dirty
syngas. Subsequently, the gas from the gas cleaning unit 110 may include
clean syngas, (e.g., the sulfur 111 has been removed from the syngas),
with trace amounts of other chemicals, e.g., NH3 (ammonia) and
CH4 (methane).

[0027]A gas processor 116 may be utilized to remove residual gas
components 117 from the clean syngas such as, ammonia and methane, as
well as methanol or any residual chemicals. However, removal of residual
gas components 117 from the clean syngas is optional, since the clean
syngas may be utilized as a fuel even when containing the residual gas
components 117, e.g., tail gas. At this point, the clean syngas may
include approximately 3% CO, approximately 55% H2, and approximately
40% CO2 and is substantially stripped of H2S. This clean syngas
may be transmitted to a combustor 120, e.g., a combustion chamber, of a
gas turbine engine 118 as combustible fuel. Alternatively, the CO2
may be removed from the clean syngas prior to transmission to the gas
turbine engine.

[0028]The IGCC system 100 may further include an air separation unit (ASU)
122. The ASU 122 may operate to separate air into component gases by, for
example, distillation techniques. The ASU 122 may separate oxygen from
the air supplied to it from a supplemental air compressor 123, and the
ASU 122 may transfer the separated oxygen to the gasifier 106.
Additionally the ASU 122 may transmit separated nitrogen to a diluent
nitrogen (DGAN) compressor 124.

[0029]The DGAN compressor 124 may compress the nitrogen received from the
ASU 122 at least to pressure levels equal to those in the combustor 120,
so as not to interfere with the proper combustion of the syngas. Thus,
once the DGAN compressor 124 has adequately compressed the nitrogen to a
proper level, the DGAN compressor 124 may transmit the compressed
nitrogen to the combustor 120 of the gas turbine engine 118. The nitrogen
may be used as a diluent to facilitate control of emissions, for example.

[0030]As described previously, the compressed nitrogen may be transmitted
from the DGAN compressor 124 to the combustor 120 of the gas turbine
engine 118. The gas turbine engine 118 may include a turbine 130, a drive
shaft 131 and a compressor 132, as well as the combustor 120. The
combustor 120 may receive fuel, such as syngas, which may be injected
under pressure from fuel nozzles. This fuel may be mixed with compressed
air as well as compressed nitrogen from the DGAN compressor 124, and
combusted within combustor 120. This combustion may create hot
pressurized exhaust gases.

[0031]The combustor 120 may direct the exhaust gases towards an exhaust
outlet of the turbine 130. As the exhaust gases from the combustor 120
pass through the turbine 130, the exhaust gases force turbine blades in
the turbine 130 to rotate the drive shaft 131 along an axis of the gas
turbine engine 118. As illustrated, the drive shaft 131 is connected to
various components of the gas turbine engine 118, including the
compressor 132.

[0032]The drive shaft 131 may connect the turbine 130 to the compressor
132 to form a rotor. The compressor 132 may include blades coupled to the
drive shaft 131. Thus, rotation of turbine blades in the turbine 130 may
cause the drive shaft 131 connecting the turbine 130 to the compressor
132 to rotate blades within the compressor 132. This rotation of blades
in the compressor 132 causes the compressor 132 to compress air received
via an air intake in the compressor 132. The compressed air may then be
fed to the combustor 120 and mixed with fuel and compressed nitrogen to
allow for higher efficiency combustion. Drive shaft 131 may also be
connected to load 134, which may be a stationary load, such as an
electrical generator for producing electrical power, for example, in a
power plant. Indeed, load 134 may be any suitable device that is powered
by the rotational output of the gas turbine engine 118.

[0033]The IGCC system 100 also may include a steam turbine engine 136 and
a heat recovery steam generation (HRSG) system 138. The steam turbine
engine 136 may drive a second load 140. The second load 140 may also be
an electrical generator for generating electrical power. However, both
the first and second loads 134, 140 may be other types of loads capable
of being driven by the gas turbine engine 118 and steam turbine engine
136. In addition, although the gas turbine engine 118 and steam turbine
engine 136 may drive separate loads 134 and 140, as shown in the
illustrated embodiment, the gas turbine engine 118 and steam turbine
engine 136 may also be utilized in tandem to drive a single load via a
single shaft. The specific configuration of the steam turbine engine 136,
as well as the gas turbine engine 118, may be implementation-specific and
may include any combination of sections.

[0034]The system 100 may also include the HRSG 138. Heated exhaust gas
from the gas turbine engine 118 may be transported into the HRSG 138 and
used to heat water and produce steam used to power the steam turbine
engine 136. Exhaust from, for example, a low-pressure section of the
steam turbine engine 136 may be directed into a condenser 142. The
condenser 142 may utilize a cooling tower 128 to exchange heated water
for chilled water. The cooling tower 128 acts to provide cool water to
the condenser 142 to aid in condensing the steam transmitted to the
condenser 142 from the steam turbine engine 136. Condensate from the
condenser 142 may, in turn, be directed into the HRSG 138. Again, exhaust
from the gas turbine engine 118 may also be directed into the HRSG 138 to
heat the water from the condenser 142 and produce steam.

[0035]In combined cycle systems such as IGCC system 100, hot exhaust may
flow from the gas turbine engine 118 and pass to the HRSG 138, where it
may be used to generate high-pressure, high-temperature steam. The steam
produced by the HRSG 138 may then be passed through the steam turbine
engine 136 for power generation. In addition, the produced steam may also
be supplied to any other processes where steam may be used, such as to
the gasifier 106. The gas turbine engine 118 generation cycle is often
referred to as the "topping cycle," whereas the steam turbine engine 136
generation cycle is often referred to as the "bottoming cycle." By
combining these two cycles as illustrated in FIG. 1, the IGCC system 100
may lead to greater efficiencies in both cycles. In particular, exhaust
heat from the topping cycle may be captured and used to generate steam
for use in the bottoming cycle.

[0036]FIG. 2 is a cutaway side view of an embodiment of the gas turbine
engine 118. The gas turbine engine 118 may use liquid and/or gas fuel,
such as natural gas and/or a hydrogen rich syngas, to operate. The gas
turbine engine 118 includes one or more fuel nozzles 144 located inside
one or more combustors 146. As depicted, fuel nozzles 144 intake a fuel
supply, mix the fuel with compressed air, discussed below, and distribute
the air-fuel mixture into a combustor 146, where the mixture combusts,
thereby creating hot pressurized exhaust gases. In one embodiment, six or
more fuel nozzles 144 may be attached to the head end of each combustor
146 in an annular or other arrangement. Moreover, the gas turbine engine
118 may include a plurality of combustors 16 (e.g., 4, 6, 8, or 12) in an
annular arrangement.

[0037]Air enters the gas turbine engine 118 through air intake 148 and may
be pressurized in one or more compressor stages of compressor 132. The
compressed air may then be mixed with gas for combustion within combustor
146. For example, fuel nozzles 144 may inject a fuel-air mixture into
combustors in a suitable ratio for optimal combustion, emissions, fuel
consumption, and power output. As discussed below, certain embodiments of
the fuel nozzles 144 include internal cooling passages configured to
provide thermal resistance to thermal damage associated with flashback
and/or flame holding. The combustor 146 directs the exhaust gases through
one or more turbine stages of turbine 130 toward an exhaust outlet 150,
to generate power, as described above with respect to FIG. 1.

[0038]FIG. 3 is a detailed perspective view of an embodiment of a
combustor head end 151 having an end cover 152 with a plurality of fuel
nozzles 144 attached at a surface 154 via sealing joints 156. In the
illustration, five fuel nozzles 144 are attached to end cover base
surface 154 via joints 156. However, any suitable number and arrangement
of fuel nozzles 144 may be attached to end cover base surface 154 via the
joints 156. The head end 151 routes the compressed air from the
compressor 132 and the fuel through end cover 152 to each of the fuel
nozzles 144, which substantially premix the compressed air and fuel as an
air fuel mixture prior to entry into a combustion zone in the combustor
146. As discussed in further detail below, the fuel nozzles 144 may
include one or more internal cooling passages configured to provide
thermal resistance to thermal damage associated with flashback and/or
flame holding.

[0039]FIG. 4 is a cross-sectional side view of an embodiment of a fuel
nozzle 144 having an internal cooling system configured to provide
thermal resistance to thermal damage associated with flashback and/or
flame holding. In the illustrated embodiment, the fuel nozzle 144
includes an outer peripheral wall 166 and a nozzle center body 168
disposed within the outer wall 166. The outer peripheral wall 166 may be
described as a burner tube, whereas the nozzle center body 168 may be
described as a fuel supply tube. The fuel nozzle 144 also includes a
fuel/air pre-mixer 170, an air inlet 172, a fuel inlet 174, swirl vanes
176, a mixing passage 178 (e.g., annular passage for mixing fuel and
air), and a fuel passage 180. The swirl vanes 176 are configured to
induce a swirling flow within the fuel nozzle 144. Thus, the fuel nozzle
144 may be described as a swozzle in view of this swirl feature. It
should be noted that various aspects of the fuel nozzle 144 may be
described with reference to an axial direction or axis 181, a radial
direction or axis 182, and a circumferential direction or axis 183. For
example, the axis 181 corresponds to a longitudinal centerline or
lengthwise direction, the axis 182 corresponds to a crosswise or radial
direction relative to the longitudinal centerline, and the axis 183
corresponds to the circumferential direction about the longitudinal
centerline.

[0040]As shown, fuel enters the nozzle center body 168 through fuel inlet
174 into fuel passage 180. Fuel travels axially 181 in a downstream
direction, as noted by direction arrow 184, through the entire length of
center body 168 until it impinges upon an interior end wall 186 (e.g., a
downstream end portion) of the fuel passage 180, whereupon the fuel
reverses flow, as indicated by directional arrow 188, and enters a
reverse flow passage 190 in an upstream axial direction. Reverse flow
passage 190 is located concentric to fuel passage 182. Thus, the fuel
first flows downstream toward the combustion zone along the axis 181 in
the axial direction 184, radially traverses the interior end wall 186 in
a radial direction relative to axis 182, and then flows upstream away
from the combustion zone along the axis 181 in the axial direction 188.
For purposes of discussion, the term downstream may represent a direction
of flow of the combustion gases through the combustor 120 toward the
turbine 130, whereas the term upstream may represent a direction away
from or opposite to the direction of flow of the combustion gases through
the combustor 120 toward the turbine 130.

[0041]At the axially 181 extending end of reverse flow passage 190
opposite end wall 186, fuel impinges upon wall 192 (e.g., upstream end
portion) and is directed into a cooling chamber 194 (e.g., a downstream
cavity or passage), as may be seen by arrow 196. Thereupon, fuel travels
from the cooling chamber 194 to an outlet chamber 198 (e.g., an upstream
cavity or passage), as indicated by arrow 200. The flow of fuel, as seen
by arrow 200, is not direct from the cooling chamber 194 to the outlet
chamber 196. Indeed, the flow is at least partially blocked or redirected
by a divider 202. The divider 202 may, for example, be a piece of metal
that restricts the direction of flow of the fuel into the outlet chamber
196, thus causing the fuel to internally cool all surfaces of the vane
176. In certain embodiments, the chambers 194 and 198 and the divider 202
may be described as a non-linear coolant flow passage, e.g., a zigzagging
coolant flow passage, a U-shaped coolant flow passage, a serpentine
coolant flow passage, or a winding coolant flow passage.

[0042]The fuel may pass around the divider 202 and into the output chamber
198, whereby the fuel may be expelled from the outlet chamber 198 through
fuel injection ports 204 in the swirl vanes 176, whereat the fuel may mix
with air flowing through mixing passage 178 from air inlet 172, as
illustrated by arrow 206. For example, the fuel injection ports 204 may
inject the fuel crosswise to the air flow to induce mixing. Likewise, the
swirl vanes 176 induce a swirling flow of the air and fuel, thereby
increasing the mixture of the air and fuel. The fuel/air mixture exits
premixer 170 and continues to mix as it flows through the mixing passage
178, as indicated by directional arrow 208. This continuing mixing of the
fuel and air through the premixing passage 178 allows the fuel/air
mixture exiting the premixing passage 178 to be substantially fully mixed
when it enters the combustor 146, where the mixed fuel and air may be
combusted. The configuration of the fuel nozzle 144 also allows for the
use of fuel as a heat exchanger medium or heat transfer fluid before it
is mixed with the air. That is, the fuel may operate as a cooling fluid
for the mixing passage 178 when, for example, flashback, (e.g., flame
propagation from the combustor reaction zone into the premixing passage
178) occurs and a flame resides in the premixer 170 and/or the mixing
passage 178. This fuel nozzle 144 is very effective for mixing the air
and fuel, for achieving low emissions and also for providing
stabilization of the flame downstream of the fuel nozzle exit, in the
combustor reaction zone.

[0043]FIG. 5 is a perspective cutaway view of an embodiment of the
premixer 170 taken within arcuate line 5-5 of FIG. 4. The premixer 170
includes the swirl vanes 176 disposed circumferentially around the nozzle
center body 168, wherein the vanes 176 extend radially outward from the
nozzle center body 168 to the outer wall 166. As illustrated, each swirl
vane 176 is a hollow body, e.g., a hollow airfoil shaped body, having the
cooling chamber 194, the outlet chamber 198, and the divider 202. The
fuel enters the cooling chamber 194 near a downstream end portion of the
swirl vane 176, travels upstream in a non-linear path about the divider
202 to the outlet chamber 198, and then exits the outlet chamber 198
through the fuel injection ports 204. Thus, the fuel flow through each
swirl vane 176 acts as a coolant prior to entry into the air flow. Again,
the fuel flow cools the swirl vane 176 along substantially the entire
length of the swirl vane 176, and provides maximum cooling at the
downstream end portion 177. For example, the fuel flow may cool at least
50, 60, 70, 80, 90, or 100 percent of the length of each swirl vane 176
along the axis 181.

[0044]In the event of flashback or flame holding in the fuel nozzle 144,
the internal cooling through each swirl vane 176 (e.g., via chambers 194
and 198) may provide thermal protection for a time duration sufficient to
take corrective measures to eliminate the flashback or flame holding. For
example, the internal cooling through each swirl vane 176 may provide
thermal protection for at least greater than approximately 15, 30, 45,
60, 75, 90, or more seconds. Furthermore, the internal cooling through
each swirl vane 176, using fuel as the coolant or heat exchanger medium,
provides a built-in failsafe in the event of thermal damage. In
particular, the thermal damage may occur at the downstream end portion
177 (e.g., downstream tip) of the swirl vane 176, thereby causing the
fuel to flow directly from the cooling chamber 194 into the air flow. As
a result, the fuel flow is substantially or entirely detoured away the
fuel ports 204 at the upstream end portion 175 of the swirl vane 176,
thereby substantially or entirely eliminating any fuel-air mixture
upstream from the thermal damage at the downstream end portion 177 (e.g.,
downstream tip) of the swirl vane 176. Thus, the thermal damage at the
downstream end portion 177 (e.g., open downstream tip) of the swirl vane
176 may reduce or eliminate the possibility of any further damage to the
fuel nozzle 144 (e.g., further upstream), though this may result in an
increase in emissions of nitrogen oxides

[0045]In the illustrated embodiment, the premixer 170 includes eight swirl
vanes 176 equally spaced at 45 degree increments about the circumference
of the nozzle center body 168. In certain embodiments, the premixer 170
may include any number of swirl vanes 176 (e.g., 4, 5, 6, 7, 8, 9, 10,
11, 12, 13 or 14) disposed at equal or different increments about the
circumference of the nozzle center body 168. The swirl vanes 176 are
configured to swirl the flow, and thus induce fuel-air mixing, in a
circumferential direction 183 about the axis 181. As illustrated, each
swirl vanes 176 bends or curves from the upstream end portion 175 to the
downstream end portion 177. In particular the upstream end portion 175 is
generally oriented in an axial direction along the axis 181, whereas the
downstream end portion 177 is generally angled, curved, or directed away
from the axial direction along the axis 181. For example, the downstream
end portion 177 may be angled relative to the upstream end portion 177 by
an angle of approximately 5 to 60 degrees, or approximately 10 to 45
degrees. As a result, the downstream end portion 177 of each swirl vane
176 biases or guides the flow into a rotational path about the axis 181
(e.g., swirling flow). This swirling flow enhances fuel-air mixing within
the fuel nozzle 144 prior to delivery into the combustor 120.

[0046]Additionally, one or more injection ports 204 may be disposed on the
vanes 176 at the upstream end portion 175. For example, these injection
ports 204 may be approximately 1 to 100, 10 to 50, 20 to 40, or 24 to 35
thousandths of an inch in diameter. In one embodiment, the injection
ports 204 may be approximately 30 to 50 thousandths of an inch in
diameter. Each swirl vane 176 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
or more fuel injection ports 204 on first and/or second sides 210 and 212
of the vane 176. The first and second sides 210 and 212 may combine to
form the outer surface of the vane 176. For example, the first and second
sides 210 and 212 may define an airfoil shaped surface as discussed
above. In certain embodiments, each swirl vane 176 may include
approximately 1 to 5 fuel injection ports 204 on the first side 210, and
approximately 1 to 5 fuel injection ports 204 on the second side 212.
However, some embodiments may exclude fuel injection ports 204 on the
first side 210 or the second side 212.

[0047]Furthermore, each fuel injection port 204 may be oriented in an
axial direction along the axis 181, a radial direction along the axis
182. In other words, each fuel injection port 204 may have a simple or
compound angle 205 relative to a surface of the swirl vane 176, thereby
influencing fuel-air mixing and varying the size of the recirculation
zones behind the fuel jets. For example, the injection ports 204 may
cause the fuel to flow into the premixer 170 at an angle of approximately
5 to 45, 10 to 60, or 20 to 90 degrees from the surface of first side 210
and/or the second side 212 of the swirl vane 176. By further example, the
fuel injection ports 204 may cause the fuel to enter the premixer 170 at
a compound angle of approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, or 60 degrees with respect to the axial direction 181. Angling the
injection ports 204 in this manner may allow for more complete mixing of
the air-fuel mixture in the premixer 170.

[0048]This premixing, as well as the curved airfoil shape of the vane 176,
may allow for a more uniform fuel air mixture. For example, the premixing
may enable a clean burn with approximately 2-3 parts per million (ppm) of
NOx (nitrogen oxides) emissions. Without nearly complete mixing of air
and fuel, peak temperatures in the reaction zone may be higher than a
uniform, lean mixture. This may lead to, for example, approximately 200
ppm of nitrogen oxides in the exhaust stream rather than approximately
2-3 ppm of nitrogen oxides in the exhaust when the fuel is substantially
mixed.

[0049]FIG. 6 is a cutaway side view of an embodiment of the premixer 170
taken within arcuate line 5-5 of FIG. 4. As illustrated in FIG. 6, the
premixer 170 may receive fuel from the reverse flow passage 190 as seen
by arrow 200. That is, the fuel may flow from the reverse flow passage
190 into the cooling chamber 194 around the divider 202 and into the
outlet chamber 198. Additionally, a bypass hole 214 (e.g., a crossover
passage) may be positioned between the cooling chamber 194 and the outlet
chamber 198. This bypass hole 214 may extend radially 182 outwards
relative to the wall 192 until it reaches the divider 202. That is, the
bypass hole 214, in effect, removes a portion of the divider 202, axially
through the divider 202, such that fuel may flow directly from the
cooling chamber 194 axially into the outlet chamber 198, as indicated by
directional arrow 215. This bypass hole 214 may allow, for example,
approximately 1 to 50, 5 to 40, or 10 to 20 percent of the total fuel
flowing from the cooling chamber 194 into the outlet chamber 198 to flow
directly between the chambers 194 and 198. Utilization of the bypass hole
214 may allow for adjustments to any fuel system pressure drops that may
occur, adjustments for conductive heat transfer coefficients, or
adjustments to fuel distribution to the injection ports 204. That is, for
example, more or less fuel may be directly transmitted to the injection
ports 204 when a bypass hole 214 is utilized in the swirl vane 176. The
bypass hole 214 may improve the distribution of fuel into and through the
injection ports 204, e.g., more uniform distribution. The bypass hole 214
also may reduce the pressure drop from the chamber 194 to the chamber
198, thereby helping to force the fuel through the injection ports 204.
Additionally, use of the bypass hole 214 may allow for tailored flow
through the fuel injection ports 204 to change the amount of swirl that
the fuel flow contains prior to injection into the premixer 170 via the
injection ports 204.

[0050]FIG. 7 is a cutaway side view of an embodiment of the premixer 170
taken within arcuate line 5-5 of FIG. 4. The premixer 170 may include all
elements of the vane 176 as illustrated in FIG. 6, absent the bypass hole
214. Thus, the divider 202 does not include a bypass to allow for the
direct transmission of fuel from the cooling chamber 194 into the outlet
chamber 198. Instead, each swirl vane 176 may include a bypass hole 216
separate from the divider 202 (i.e., not between chambers 194 and 198) to
allow fuel to flow directly into the outlet chamber 198 from the fuel
passage 180 (i.e., not from the fuel passage 190), as indicated by
directional arrow 218. Again, this bypass hole 216 may allow for
approximately 1 to 50, 5 to 40, or 10 to 20 percent of the total fuel
flowing through the injection ports 204 to flow into the outlet chamber
198. This may allow for, again, direct control over the amount,
distribution, and direction of fuel flowing into the injection ports 204
and also control the amount of fuel traveling the lengths of passages 180
and 190. Likewise, the bypass hole 216 may substantially reduce the
pressure drop from the chamber 194 to the chamber 198, thereby helping to
force the fuel out through the injection ports 204. In a further
embodiment, a bypass hole 216 may allow fuel to flow directly into the
cooling chamber 194 from the fuel passage 180, instead of or in addition
to the bypass hole 216 that allows fuel to flow directly into the outlet
chamber 198 from the fuel passage 180.

[0051]FIG. 8 is a cutaway side view of an embodiment of the premixer 170
taken within arcuate line 5-5 of FIG. 4, further illustrating a
combination of the embodiments illustrated in FIGS. 6 and 7. As
illustrated in FIG. 8, each swirl vane 176 may include both a bypass hole
214 from the passage 190 and a bypass hole 216 from the passage 180. In
this manner, the bypass holes 214 and 216 may route between approximately
5 to 60, 10 to 50, or 20 to 40 percent of the total fuel to enter the
injection ports 204 directly into outlet chamber 198 without first
passing through the cooling chamber 194 and around the divider 202. In
this manner, more fuel may be directly passed to the injection ports 204,
which may allow for better control of the fuel injected into the premixer
170 and control of the fuel pressure loss. However, as a trade off, the
reduced fuel flow along directional arrow 200 may not cool the vane 176
as thoroughly.

[0052]It should be noted that the fuel as it passes through the vane 176
may be approximately 50 to 500 degrees Fahrenheit. In contrast, syngas
may burn at a temperature of approximately 3000 degrees Fahrenheit.
Accordingly, the cooling of the materials utilized in manufacturing the
premixer 170 via the fuel in the vane 176 may allow the premixer 170 to
continue to function when exposed to burning syngas for a short period,
for example, approximately 15, 30, 45, 60, 75, 90, or more seconds. The
material utilized to manufacture the premixer 170 may be, for example,
steel, or an alloy containing cobalt and/or chromium. One manufacturing
technique that may be used to manufacture premixer 170 is a direct metal
laser sintering process. Other manufacturing methods include casting and
welding or brazing. By utilizing the fuel as the cooling medium for both
the premixer channel 178, as well as the vanes 176, a held flame may be
sustained for up to a minute in the passage 178, without damaging the
fuel nozzle 144. That is, the flame that typically resides approximately
0.5-2 inches past the downstream end of the fuel nozzle 144 into the
combustion chamber of the combustor 146 may, due to the high reactivity
of the syngas (particularly the hydrogen in the syngas), flashback into
the passage 178 to the premixer 170. This occurrence may be monitored,
and by cooling the elements of the fuel nozzle 144, a user or an
automated control system may have up to a minute to eliminate the held
flame in the premixer by a method including, but not limited to, reducing
fuel flow, increasing air flow, or modifying the composition of the fuel
to the nozzle 144.

[0053]In this manner, no additional cooling fluid is required to be
introduced into the fuel nozzle 144 to aid in reducing flashback damage
in the fuel nozzle 144, because the fuel may act as a heat exchanger
fluid for reducing the overall temperature to which the passage and the
premixer 170 are exposed. Additionally, by including the divider 202 in
the vanes 176, fuel may flow through the entire interior portion of the
vanes 176, thus providing a coolant flow as a heat exchanger in cases of
flashback into the premixer 170. In this manner, instead of a flashback
destroying, for example, the vanes 176 in the premixer 170 due to
exposure to the high heat (e.g., approximately 2000 degrees Fahrenheit),
the overall temperature is reduced by the heat transfer occurring inside
the premixer 170 via the fuel passing through the vanes 176 and the
reverse flow passage 190. This may reduce the temperature that the
premixer 170 is exposed to, thus allowing the premixer 170, as well as
the vanes 176 therein, to resist damage via flashback or held flame in
the premixer 170

[0054]This written description uses examples to disclose the invention,
including the best mode, and also to enable any person skilled in the art
to practice the invention, including making and using any devices or
systems and performing any incorporated methods. The patentable scope of
the invention is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they have structural elements
that do not differ from the literal language of the claims, or if they
include equivalent structural elements with insubstantial differences
from the literal languages of the claims.